Filter protection



FILTER PROTECTION Filed Feb. 11, 1938 83 o r/Tr m 6 Z J l INVENTOR (SIarenceWNes sell BY /W mu ATTORNEY Patented May 1939 UNITED STATES PATENT OFFICE Minneapolis-Honeywell Regulator Gompany, Minneapolis, Minn., a corporation of Delaware Application February 11, 193i, Serial No. 1",!

The present invention relates generally to warm air heating systems and pertains more particularly to the elimination of the fire hazard attendant to the use of combustible air filters in such 5 systems.

In present warm air heating systems, it is customary to employ filters toremove foreign matter such as dust and dirt and the like which may contaminate the air in rooms being heated and 10 be carried into the return air registers. Fans are employed to provide an enforced circulation of air and inasmuchas the trend in furnace design is toward compactness, the filters are usually located in the return air section of the furnace 1 which houses the fan as well. Filters as ordinarily used are made of combustible material and become coated with inflammable dust and debris and being located in close proximity to'the furnace proper-there is grave danger of their becoming ignited and setting the building on fire. The existence of this danger is plain and its seriousness is apparent inasmuch as the return air ducts frequently are formed in part from the wooden joists and flooring of frame buildings.

u The danger of igniting'the filters and consequent fire hazard to the building is particularly serious when an.ecihom izer" or a "preheater is used. The econominer consists of a tortuous passageway for coinveyinggases of combustion to the stack or flue and is located in he path of the return air for the P p of preheating same. The "economiaer" normally becomes quite hot and in compact furnace designs is located close to the filters and increases the danger of w setting the filters on fire. The danger is especially present when the furnace fan is not operxin The primary object of my invention is to eliminate the above described fire hazard by providing 0 means to limit the value to which the temperature adjacent the filters in a warm air heating system may rise.

Another object of my invention is to provide a positive acting'device for automatically moving the filters in such a mannerto preclude their becoming ignited when such danger exists. In' connectiomwith the previously stated object, it is a further obiect oi'athe invention to cause the furnace fantobecome automatically a energized when danger of ignition of the filters occurs. The enforced circulation of air produced by the fan will operate to carry heat from the filters tending to reduce their A further object of my invention is to provide a filter deviceautomaticaliyoperable to: move substantially out of the air stream and the path of radiant heat flow from the furnace or "economizer" when danger of ignition occurs. The accomplishment of this objective results in the obstruction to the air stream formed by the filters I being removed and the heating of the filters due to radiation from the furnace and economiser being greatly decreased.

A still further object of my invention is to provide a collapsible filter arrangement normally held in position by springs and a fusible link operative to collapse in response to a predetermined temperature causing said link to fuse.

Further objectives and purposes of the invention will become apparent from a perusal of the drawing and the more detailed description following.

The single figure represents somewhat diagrammatically the principal portions of a warm air heating system having an oil fired furnace no -controlled primarily by a room thermostat, and

my improved filter protection and control arrangement incorporated therein.

Referring to the drawing, reference numeral ll indicates generally a furnace casing forming as a part of a warm air heating system. Casing II is divided into three separate compartments numbered ii, i2, and II, compartment II being the heating chamber and compartment ll forming a return 'air chamber. Conduits II and ii 80 communicate with compartments li and it, respectively, for conveying heated air from the furnace to the spaces to be heated and back to the furnace. Conduits II and II may have branch conduits as shown at It and II for conveying air as to and from individual rooms of a building being heated.

Compartment ll of the furnace casing houses an oil burner of conventional type indicated at 20, the nozzle of which extends through the compartment l2 into the combustion chamber proper indicated at II. The burnt gases of combustion from the chamber it pass through a device indicated at I! commonly known as an economiaer. The economizer 22 comprises a casing having an 5 arrangement of internal bailles asshown whereby p a tortuous passageway is formed for the gases as they p 8 to the stack or line at It. The economizer 22 is located within the return chamber it so that the return air passes in heat exchange relation with the economirer and is therefore preheated before being passed through the heating chamber proper It. At the lower part of the return air chamber I8 is a fan or blower II of conventional type driven by an electric motor it u by means of a belt 21 or other suitable drivins means. The fan 25 within the chamber it forces air through a discharge conduit 25 into the heating chamber l2 and past the furnace or combustion chamber 2!.

Within the upper portion of the return air chamber is is a series of filter members 3| arranged in the path of the return air stream for the purpose of removing any foreign matter with which the air being circulated may have become contaminated in the rooms being heated. The fllter members 3| include two outer members hinged at points 32 and having their inner edges biased towards the side walls of the portion 80 of the chamber I! by tension springs 33. The two inner members 3| are secured to a hinge member 35 which is rigidly pivoted at 36. The upper edges of the two inner members 3i may engage with angle members 31 attached to the upper edges of the outer members 3! as shown. The tension spring tends to draw the inner member ll towards each other around the pivot point 55 but it is prevented from doing so by reason of their engagement with the angle members 31. It is obvious that should the tension springs 33 be permitted to draw the outer members 3| toward the side walls of the chamber IS, the two inner members 3i will be drawn together by the spring 50. The filter members are retained in the position shown by means of links 4| which are pivoted to the outer members ll and which engage at their lower ends with the horizontally arranged links 42. The links 42 are constrained to move in a horizontal direction by retaining elements and are each biased towards the side walls of the chamber l3 by tension springs 44. The inner ends of the link members 42 are connected by a fusible link 45 which will fuse at a predetermined temperature in the region adjacent to the filter members and the fusible link. It is obvious that when the fusible link 45 fuses, the tension springs 44 will draw the links 42 outwardly freeing them from engagement with the links ll andwill thus permit tension springs 32 to disengage the outer members 21 from the inner members 3| and draw them towards the side walls of the chamber l3. When this happens, the tension spring 40 will draw the upper edges of the inner members 3| together thus causing all of the filter members to be substantially drawn out of the air stream. This collapsible arrangement of the filters is an important feature of the present invention inasmuch as the filters automatically collapse and remove themselves from the path of radiant heat from the economizer 22 at a predetermined temperature at which there is danger of their becoming ignited.

The link 42 on the left, as seen in the drawing, is connected as shown to a lever carryin a double ended mercury switch 5|. Normally, the e cury switch ii is in the position shown in the drawing. Obviously, when the fusible link 45 fuses, tension spring 4| attached to the link 42 on the left will cause lever 50 to be rotated counterclockwise and will cause the contacts in the left end of the mercury switch 5| to be made and those in the right end of the switch to be broken.

The system is primarily controlled by a room thermostat generally indicated at 55. This thermostat comprises a circularly arranged bimetallic element 56 of conventional type having a movable arm 51 arranged to make or break anelectrical circuit through a fixed contact 58. Further control is provided by a pair of mercury switches 55 and 5! operated by a helical thermostatic element 62 responsive to the temperature of.the air being heated within the chamber l2. The thermostatic element 82 is arranged to close the switch ii at a predetermined relatively low temperature in the chamber l2 and to open the switch 50 which is normally closed at a predetermined relatively high temperature in the chamber l2 beyond which it is not desired that the temperature should rise.

Power for the system is supplied through a pair of line conductors I0 and 1| connected to an external source of power (not shown). The burner 20 is driven by an electric motor and energy for the motor is supplied through a wire 12, a wire ll-wire ll connecting to a pilot controlled safety device 15, a wire 16 connecting to the mercury switch il, a wire ll connecting mercury switch 50 to the thermostatic switch 55, a wire I8 connecting the thermostatic switch to the right end of mercury switch 5|, and. a connection from the right end of mercury switch iii to the line conductor Ill. The pilot controlled safety device I5 is of conventional type and comprises a bimetallic element Bl arranged adjacent the pilot burner 5| so as to complete its circuit through the fixed contact 82 at all times when the pilot flame is burning. A pipe 83 communicates with the source of combustible gas providing fuel for the pilot flame III which is keptconstantly burning for purposes of igniting fuel injected into the combustion chamber through the nozzle of burner 20. The extinguishment of the pilot flame 2| obviously causes the power supply circuit for the burner motor to be broken.

Power for the fan motor 25 is supplied from line conductor ll through a conductor 12 to the motor, a wire 85 from the motor to the mercury switch 5!, and a wire 86 from the mercury switch 5| to the line conductor Ill. Obviously, whenever the mercury switch BI is closed the fan motor 26 will be energized and the fan 25 enforces a positive circulation of air through the system. The fan motor 26 may also be energized when the mercury switch ii is tilted to the left by a circuit from line conductor Ill through the left end of the mercury switch H to a wire 58, through the wire 85, through the motor and through wire 12 back to the line conductor 1|.

From the foregoing description the operation of my system and the manner of control should be apparent to those skilled in the art. With the parts in the position shown in the drawing, the thermostat is satisfied and neither the burner 20 nor the fan motor 25 are operated. Should the room or space temperature fall to a predetermined value indicating that heat should be supplied to the spaces being heated, the thermostatic switch device 55 closes completing the above described electric circuit through the burner motor. When the temperature within the heating chamber l2 has risen to a predetermined value, mercury switch 5| will close, energizing the motor 25 causing the fan 25 to begin positively circuating air through the system. It will be seen that this air is drawn through the filter members 2| and is preheated as it passes over the economizer 22 before being forced into the heating chamber l2. The economizer temperature may rise to a relatively high value and considerable heat is radiated therefrom which is normally imparted to the air being circulated past the eccnomizer. Should the fan 25 now stop due to breakage of the felt 21, or if the temperature adjacent the filter should for any other airmen from said heater at a predetermined temperature reason. rise to a predetermined value at which there is danger of igniting the filter material. the fusible llnk ll fuses. when this happens.

.the filter members II collapse in the manner above. described and at the same time the mercury switch II a is tilted to the left breaking the electrical circuit through the burner motor and .at the same time completing a circuit through the left end of the mercury switch to the fan motor. Attimes, the temperature adjacent the filter members It may rise to an unsafe value before the temperature in the heating chamber I! has risen to a high enough value to cause closure of switch ii. The fan It will, therefore not be operating at the time fusion of link It takes place. However, in anysystemby reason of the double ended mercury switch ll. operation of the fan will be initiated at this time and will operate to positively circulate air over the economizer 22 and will tend to diminish its temperature. In practice, filter members such as the members if as ordinarily employed present considerable surface to exposure from radiant heat from the economizer and thus as the oonomlaer temperaturerises the filter temperature rises accordingly. By my collapsible arrangement of the filter members, their surfaces are automatically removed from exposure to radiant heat from the economizer and they are positioned so as not to obstruct the passage of air over the economizer. The double ended-mercury switch 5| provides an additional safety feature which eliminates the danger of combustion taking place in the filters in the event that the economizer should reach an unsafe temperature value before operation of the fan 26 has begun. My improved arrangement eliminates a serious fire harard attendant to the use of filters especially when employed in compact furnace designs as at present in use. Its simplicity and sturdiness make its use very economical and additionally, being easy of installatiom'it is an appliance which may be universally utilized in present existing warm air heating systems.

While one embodiment of the invention has been disclosed, there are many variations and modifications and forms which the invention may take and it is to be understood that'the present disclosure is to be interpreted as illustrative only and the scope of the invention to be limited only as determined by the appended claims.

I claim as my invention:

1. In a warm air heating system, in combination, heating means, means for circulating air to be heated past said heating means, filter means for cleaning said air exposed to heat from said heating means, said filter means being collapsibly supported and normally latched in non-collapsed position by means including a temperature responsive element so arranged that at a predetermined temperature adiacentsaid filter means the filter means will be automatically removed from exposure to heat from said heating means whereby danger of ignition of the filter means iseliminated.

a. In a heating system, in combination...- a heater, means for circulating air to be heated past said heater, collapsible filter means for cleaning said air exposed to radiant heat from said heater, means including spring latches and a temperature responsive element adjacent filter means for causing said filter means to collapse substantially out of the path of radiant heat of said temperature responsive element.

a. Ina heating system, in combination, a heater, means for circulating air past said heater. filter means for cleaning said air exposed to heat from said heater. said filter means comprising hinged portions retained in position by means including spring members and a fusible link. said link being located adjacent said filter means said filter means being arranged to move in such a way as to expose insubstantial surface to heat from said heater at a predetermined temperature causing said link to fuse.

4. In a heating system in combination a furnace having a casing. ,means for circulating air to be heated through said casing. filter means for cleaning air located in said casing adjacent a part of said furnace and exposed to radiation of heat from said furnace part, means including a temperature responsive element adjacent said filter means for abruptly moving said filter means substantially out of the path of heat radiated from said furnace part at a predetermined temperature afiecting said temperature responsive element. v

5. In a heating system, in combination, a furnace having a casing. a fan for circulating air to be'heated through said casing, filter means for cleaning said air located in a part of said casing exposed to heat from said furnace, means operable at a predetermined temperature adiaoent said filter means for substantially removing them from exposure to heat from said furnace and for simultaneously starting said fan for circulating air past said filter means.

8. In a heating system, in combination, a furnace having a casing, a fan for circulating air to be heated through said casing, filter means for cleaning sir located in a part of said casing exposed to heat from said furnace, means operable at a predetermined temperature adjacent said filter means for substantially removing them from exposure to heat from said furnace. and means actuated upon removal of the filter means for starting said fan and cutting off the heat supply to said furnace.

7. In a heating system, in combination, a furuses including a casing having a return air chamber. an economizer comprising a tortuous passageway for burnt gases of combustion in said return air chamber, means for circulating air through said' casing over said eeonomizer and filter means for cleaning said air located adjacent said economiaer, said filter means comprising a collapsible arrangement of hinged memhere, means for retaining said filter means in normal position comprising spring members and a fusible link adjacent said filter means, said retaining means beingarranged to cause said hinged members to collapse to protect them from radiant heat at a predetermined temperature causing said link to fuse.

8. In a heating system, in combination, a furnace including a casing having a return air her, an economiser comprising a tortuous passageway for burnt gases of combustion in said return air chamber, means for circulating air throu h said casing over said economiser and filter means for cleaning said air located adiacent said eoonomiler, said filter means comprising a collapsible arrangement of hinged members, means for retaining said filter means in normal position comprising spring members and a fusible link adjacent said filter means. said etaining means being arranged to cause said hinged members to collapse to protect them from radiant heat at a predetermined temperature causing said iink to fuse, and switch means operable upon fusion of said link to start said air circulating means and to cut oil the heat supply to the furnace.

9. In a heating system, in combination, heating means, means for circulating air to be heated over said heating means, filter means for cleaning air normally exposed to heat from said heating means, said filter means being susceptible to becoming overheated and being substantially removable from exposure to heat from said heating means, and means responsive to a condition indicating that said filter means may become overheated for abruptly and substantially removing said filter means from exposure to heat from said heating means.

10. In a heating system, in combination, heating means, means comprising a fan for circulating air to be heated over said heating means, filter means for cleaning air normally exposed to heat from said heating means, said filter means being susceptible to becoming overheated and being substantially removable from exposure to heat from said heating means, and means responsive to a condition indicating danger that said filter means may become overheated for substantially removing said filter means from exposure to heat from said heating means, and for causing operation of said fan for transporting heat away from the vicinity of said filter means.

11. In a heating system, in combination, heating means, means for circulating air to be heated over said heating means, filter means for cleaning air having a normal position exposed to heat from said heating means, said filter means bein susceptible to becoming overheated, means comprising a fusible link whereby at a predetermined temperature causing said link to iuse, said filter means are substantially removed from exposure to heat from said heating means.

CLARENCE w. NESSELL.

CERTIFI GATE OF CORRECTION Patent No. 2,159,951.

, CLARENCE W. NESSELL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 75, claim 2, before the word "filter" insert said; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 21st dav of November, A. D. 1959.

(Seal) Henry Van Arsdale,

Acting Commissioner of Patents.

hinged members to collapse to protect them from radiant heat at a predetermined temperature causing said iink to fuse, and switch means operable upon fusion of said link to start said air circulating means and to cut oil the heat supply to the furnace.

9. In a heating system, in combination, heating means, means for circulating air to be heated over said heating means, filter means for cleaning air normally exposed to heat from said heating means, said filter means being susceptible to becoming overheated and being substantially removable from exposure to heat from said heating means, and means responsive to a condition indicating that said filter means may become overheated for abruptly and substantially removing said filter means from exposure to heat from said heating means.

10. In a heating system, in combination, heating means, means comprising a fan for circulating air to be heated over said heating means, filter means for cleaning air normally exposed to heat from said heating means, said filter means being susceptible to becoming overheated and being substantially removable from exposure to heat from said heating means, and means responsive to a condition indicating danger that said filter means may become overheated for substantially removing said filter means from exposure to heat from said heating means, and for causing operation of said fan for transporting heat away from the vicinity of said filter means.

11. In a heating system, in combination, heating means, means for circulating air to be heated over said heating means, filter means for cleaning air having a normal position exposed to heat from said heating means, said filter means bein susceptible to becoming overheated, means comprising a fusible link whereby at a predetermined temperature causing said link to iuse, said filter means are substantially removed from exposure to heat from said heating means.

CLARENCE w. NESSELL.

CERTIFI GATE OF CORRECTION Patent No. 2,159,951.

, CLARENCE W. NESSELL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 75, claim 2, before the word "filter" insert said; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 21st dav of November, A. D. 1959.

(Seal) Henry Van Arsdale,

Acting Commissioner of Patents. 

